Automatic telephone system



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6 Sheets-Sheet 4 N. H. SAUNDERS AUTOMATIC TELEPHONE SYSTEM Filed May 19, 1934 1E.; HQ, i935. N. H. sAUNDERs AUTOMATIC TELEPHONE SYSTEM Filed May 19, 1934 6 Sheets-Sheet 5 smh.

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6 Sheets-Sheef 6 Filed May 19, 1954 f N vE/vToR- /Vofrm/v H. 5A unos/es Arrrj no uw Patented Dec. 10, 1935 UNITED ANT OFFIQE UTOMATC TELEPHONE SYSTEM Application May 19, 1934, Serial No. '726,501

20 Claims. (Cl. 179-17) This invention relates in genera-l to automatic telephone systems, but more in particular to small systems suited for installations in towns or villages. An automatic telephone system of this type is generally known as a community automatic exchange or C. A. X., and may have a capacity of fifty lines, more or less. Usually the lines are party lines having either bridged or grounded ringing circuits over which the subscribers are signalled by means of code ringing. Provision is made also for trunking calls to and from distant exchanges.

The object oi the present invention is to provide a novel and improved all relay community automatic exchange of the foregoing character.

One ci the features of the invention relates to the novel circuit arrangement in the all-relay finder connector link for interconnecting the various lines in this system'.

Another feature of invention relates to an improved lock-pulse arrangement for repeating impulses.

Another feature of the invention relates to the circuit arrangements for selecting and connecting various code rings to called subscribers lines to signal a particular subscriber thereon dependent on both the line and code selecting digits dialled.

Another feature relates to the novel start and transfer circuit arrangement for allotting the various links for use, for transferring a call from one line to another in case the nder-unit relays of the rst link fails to find the `calling line, and for preventing a link, just released, from stealing a call away from another link.

These and other features of the invention will be apparent from the following detailed description of the invention.

Referring now to the drawings, comprising Figs. l to 6, inclusive, there is shown by means of the usual circuit diagram one of the all-relay finder connector links, the different line circuits and substation circuits by means. of which the invention may be described and understood.

Fig. l shows a party line, in this case line il and its associated line circuit. The line conductors i4 and i5 and the incoming test conductor it of this line, shown bracketed, extend to the connecting end of the nder connector link in Fig. 4 Where the conductors connect with correspondingly numbered conductors. The remainder of Fig. l shows the nding end of the finder connector link comprising a set of finder group relays FGR and finder unit relays FUR. Each group of lines, such as the ten group has two 5 nder group relays, such as relay l lil for connecting only the line conductors of line group lll to the link, and relay lil which connects only the test conductors of line group i@ to the link. It is assumed in this case that there are eight groups of lines, each comprising seven lines each. ln order to simplify the drawings, only three groups of lines, namely the lli-group, Ztl-group, and iQ-group have been shown` Each of the lines are connected to a line circuit in the same manl5 ner as illustrated for line El. The nder unit relays FUR correspond in number to the number of lines in each group, in this case, since there are seven lines in each group there are seven iinder unit relays. Only three of the finder unit relays, however, have been shown in order to simplify the drawings.

Figs. 2 and 3 show the control relays oi this nder connector link.

Fig. 4 shows the connecting end ci this finder 25 connector link and two line circuits. in 'the same manner as described for the nder group relays the connecting end of the link includes two relays for each group of lines. The connector group relay MG for the first or tens group connects only the line conductors of the lines in the ilgroup to the link while the relay al l connects only the test conductors of the line in the i-group to the link. Sincethere are eight groups of lines then there are eight sets of connector group relays provided, but only four of such sets have been shown. The connector unit relays comprise a group of seven relays, one relay for each corresponding line in a group. In this case only four of the connector unit relays are shown in order to reduce the drawing. Each cdd connector unit relay prepares a circuit for the succeeding even connector unit relay, and each even connector unit relay prepares a circuit for the succeeding odd connector unit relay, as diagrammatically illustrated by the dotted lines. In a similar man* ner each oif connector group test relay, such as relay ci! i, prepares a circuit for the succeeding even connector group test relay, such as relay 42E. In a similar manner each even connector 50 corresponding connector unit relays.

group test relay such as relay 62| prepares a cir cuit for the succeeding oddr connector group test relay, such as relay l i, not shown. In the upper right-hand corner is shown the line circuit forV party line 1|. The subscribersringers on this line arerconnected to both the negative and posi tive line Vconductorsfto provide the so-called di vided ringing. Inthe lower right-hand corner of Fig. 4 is shown the line circuit of a grounded twenty-party party line.

Fig. 5 in its upperV portion diagrammatically illustrates the chain circuit arrangement between the Various finder connector links in this system while relays 56E? t0 5W, inclusive, comprise the allotting vand alarm relays. TS diagrammatically illustrates a time switch which' is started in response to the Yoperation of start relay 5|D to close springs 592 and 503 at pree determined time intervals. Relays 585 and 590 and interrupter 593 comprise a timing device for freeing a finder connector link in case the same is held by a permanent line. y Y

Fig. 6 shows the code selecting relays CSR `which are. controlled by the impulse repeating relay in the link to selectively connect one lof the code ringing'conductors extending to aringing interrupter, not shown. chine, not shown, is started in operation in responseto the operationfof a switching relay in any link circuit and periodically grounds the code ring conductors-shown to produce codes indicated by the numerals associated with such conductors. Y

Briefly, the operation of this system is as follows: When a calling subscriber initiates a call the test conductor of Vthe calling line is marked with calling potential and the calling group is marked in all the finder group relays in all the links. The start conductor is grounded and the finder group relays in the first idle link operate in sequence to find the calling group. When the calling group is found the Ylast operated finder group relay connects the test conductor of all the lines in the calling groupr to the nder units relay, which now operates in sequence until the marked calling line is found.

' When the calling line is found the transfer relay in the link is'operated to prepare another idle link for use and the calling line is connected to the control circuit of the link in use. The first digit transmitted by the calling subscriber operates an impulse repeating relay to successively operate the connector group relays. Only the last operated connector group relay is maintained energized to connect the test conductor of the called group to the connector units relays of the link. The second digit reoperates the impulse repeating relay to successively operate the Only the last operated connector unit relay is maintained energized to connectthe test conductor `of the called line to the link control circuit. TheV third digit reoperates the impulse repeating'relay to rthe selected code ringing conductor Vto cause the bells on the called line to be rung'in accordance V with the code selected. Y

In outgoing trunk calls the calling line is found in the same manner as just described and in response to dialling the two digits designating a trunk call the corresponding connectorV group and unit relays operate as before to connect The ringing mal Local calls It will now be assumed that subscriber S in Fig. 1 desires to call subscriber S4 shown in Fig. 4. When subscriber S removes his receiver a circuit is completed for energizing line relay I over the following circuit: from ground by way of armature l0 and resting contact, lower winding of line relay I, line conductor I5, through the substation loop over line conductor I4, armature 8 andrthrough the upper winding of relay |to battery; at armature 5, relay I connects calling potential to the test conductor by way of armature and the winding of cut-olf relay 2; at armature 5 and resting contact discon- Lnects the cut-off relay 2 from the incoming test the winding of start relay 5|() to battery. At 2 armature 5I| relay 5|6 completes a circuit for energizing line relay 25T; at armature 5|2 prepares the locking circuit for relays 540, 550 and 555; at armature 5|3 completes the circuit for energizing relay 52B, and at armature 5|4 prepares a circuit for sliunting relay 520 and for energizing relay 530. The circuit for energizing relay 520 extends from ground through winding of relay 52|), armaturesvIS, 533, and 544, resistance 546 to battery. Relay 525, upon energizing, at armature 52| prepares a circuit for energizing relay 530 and at armature 523 connects the winding of relay 560 to the time switch TS. Relay 535 is not energized at this time because this relay is shunted over the following circuit: I from batteryV through the resistance 545, armatures Y 555i, 533, EIS, and 52| to the Winding of relay 53,5 and battery. Y

Line relay 297 energizes over the following circuit; ground by way of armature 55|, armature 5II, resistance 5i5, armature 53| and resting contact, IN start lead 28|, armature 2| 5 and resting contact, conductor |50, armature 246 andY resting contact, upper left-hand Winding of repeating coil RC, normally closed springs controlled by armature 233 and through the winding of line relay 2li? to battery. At armature 238 relay 257 completes the circuit for energizing impulse repeating relay 363, and at armature 23| prepares the circuit for energizing relay 30 The circuit fork energizing impulse repeating relay 353 may be traced as follows: from ground by way'ofarmature 249 and resting contact, conductor 252, armature 32! and resting contact, conductor 26|, armature 23B, conductor 250, and through the `winding of impulse repeating relay 3F33 to battery. At armature 324 and working cntactrelay 3D3 completes a holding circuit for itself by Wayof resistance 329 and conductor 26 I; at armature 335 completes an obvious circuit for energizingrelay 39| and grounds conductor 264; at armature 325 opens a point in the circuit to relays 355, 3231 and 399,' and at armature 321 shunts armature 238. At armature 3|6 relay 33| prepares a high resistance circuit for line relay 287, at armature 5 Il prepares a circuit for switchthrough relay Els, and at armature 3|8 grounds conductor V2li to complete a circuit for energizing slow toV release relay 352, as follows: from ground by way of armature 3I8, conductor 21|,

through armatures 239 and 226 in multiple to conductor 212 and through the winding of relay 302 to battery.

At armature 329 and resting contact relay 302 opens the original energizing circuit of relay 303 which is now held energized over its locking circuit from ground at armature 324. At armature 320 and working contact relay 302 grounds conductor 253 and closes a multiple ground circuit though relay 30| by way of armature 23| and working Contact and conductor 264. At armature 32| relay 302 grounds conductor 265 to prepare a circuit for the disconnect relay 206, at armature 322 connects grounded conductor 215 to finder lock conductor |53 and completes a circuit for energizing the rst nder group relay lll, and at armature 323 grounds the connector lock conductor 218 as well as lock conductor 219 by way of armature 24|.

The circuit for energizing the rst finder group relay extends from grounded conductor |53, armature 223 and resting contact, armature 22|! and resting contact, conductor |56, resistance armature |81 and resting contact, through the armatures and resting contacts of the nder group relays, not shown, to armature |21, resting contact of armature |21, armature ||1 and resting contact, through the winding of relay to battery. At armature |B, relay completes its own locking circuit through the resting contacts of armatures, such as armatures |25 and |85, on the finder group relays to grounded conductor |53; at armature HB prepares the circuit for relay H5; at armature ||9 connects the grounded start lead 6| to the group test relay 253 by Way of conductor |59 and armature 224; at armature ||1 and resting contact opens its original energizing circuit and at its working contact closes the circuit for the second finder group relay |2|. Relay such as relays |2| and |8| are slightly slow to operate on account of their slugs and the resistance |99. At the upper armatures of relay the test conductors of the lG-line group are connected to the test armatures of the finder units relay.

in order to describe the operation of the nder group relays it will be assumed for the time being that the calling line is not in the rst or the lO-line group. ln this case, after an interval relay i2! energizes over the following circuit: from grounded lockconductor |53, by way of armatures 223 and 22|) and their resting contacts, conductor |55, resistance |98, armatures and resting contacts of the finder group relays to armature ||1 and its working contact and through the winding of relay |2| to battery. In a manner similar to that described for relay relay |2| energizes and at armature |26 locks itself to grounded conductor |53. At armature |25 relay |2| opens the locking circuit of relay whereupon the latter relay deenergizes after an interval, and at armature |21 opens a point in its original energizing circuit and at the working contact of armature |21 completes the circuit for the succeeding nder group relay associated with the ISO-line group, not shown. At armature |28 relay I2! prepares the circuit for relay |22, at armature |29 connects the start lead 22 of the ZG-line group to the group test relay 253, and at its upper armatures connects the test conductors of the 20-line group to the iinder units relay. Relay i, upon deenergizing at its upper armatures disconnects the test conductors of the lO-line group, at armature H8 opens the prepared circuit to relay |||3 and at armature H9 disconnects the start lead 6| from the group test relay 263. Finder group relays |3| to |1|, inclusive (not shown) and relay |8| operate in the manner just described, each succeeding relay opening the locking circuit to the preceding relay toA deenergize the same, connecting the corresponding group start lead to the group test relay 253, preparing a circuit to its associated line connecting relay, completing its own locking circuit, and connecting the test conduotors of its associated group to the finder units relay.

When the nder groupl relay corresponding to the group in which the calling line is located is operated ground on the start lead completes the circuit for energizing the group test relay 203. For example, relay at armature I9 completes the circuit for energizing group test relay 223 in case a line in the ||3line group is calling as follows: from grounded start lead 6|, armature H9, conductor |53, armature 224 and through the lower winding of group test relay 203 to battery. At armature 2|8 relay 253 completes a short circuit around its upper winding to make this relay slow to release, at armature 2|$ opens a point in the circuit to relay 262, at armature 22B disconnects grounded conductor |53 from conductor |55 to open the circuit to the succeeding finder group relay before the same can energize and close its locking circuit, and at armature 22|) and working contact connects the grounded conductor |53 to conductor |55 for energizing the rst finder unit relay EDI as follows: from grounded conductor |53, armature 223 and resting contact, armature 226 yand working contact, conductor |55, armature |22 and resting contact, armature |25 and resting contact, through similar armatures on the finder unit relays (not shown) to armature |28 and resting contact and through the Winding of relay lili to battery. At armature |4| relay completes a locking circuit for itself by way of armatures on the other flnder'unit relays (not shown) to grounded conductor |53. At armature |42 relay ||J| opens its original energizing circuit and completes the circuit for relay |02 and at its upper armatures connects the link line conductors |50 and |5| to contacts on the finder group relay and at armature |55 connects the test lead |52 to the test lead I9 of line to prepare a circuit for the line test relay 2M.

The finder unit relays, due tothe copper slug on their' upper ends, are fairly slow to operate, and therefore the second nnder unit relay only operates after a time sufficient to permit the energization of the line test relay 294 in case a calling line is connected with. In case line is not a calling line, then relay |82 energizes after an interval by way of grounded conductor |55, armature |52 and working contact. At armature |43 relay |52 opens the locking circuit of relay which accordingly deenergizes after an interval, at armature |44 completes a locking circuit for itself from grounded conductor |53, at armature |45 and working contact prepares the circuit for the third nder unit relay not shown) and at its upper armatures connect the line conductors |55 and |5| to the line finder group contacts and at armature |22 connects the test conductor of line 2, since relay associated with the |6- line group is energized, to the test conductor |52.

Relay |!l|, upon deenergizing, at its upper armatures disconnects the test and line conductors at armature 1| opens a point in its own locking circuit, at armature |42 and workingv contact opensthe original energizing circuit of relayl2, and at the resting contact of armature |42 Vconnects the third nder' unit relay (not shown) to grounded conductorV |55, by way of amature |45 and its working contact. Finder unit relaysY |03 to |05, inclusive (not shown) and relay |01 operate in themanner just described, each relay at its upper armature connecting the Vtest conductor of its correspondingline to'line test relay 254, opening the locking circuit ofthe preceding operated relay, closing its own locking circuit, and preparing the energizing circuit tothe succeeding relay which is completed when the preceding relay deenergizes.V

In this case, since line |1 is calling, then when iinder unit relay |31 energizes this relay at armature |14 completes the 'circuit for energizing the line test relay`24 in series with the cut-oli relay 2 as follows: from ground at armature 3 I8, conductor 21|, upper Winding of line test relay 204, conductor |52, armature |14, armature ||4, armature 5, armature and Vthrough the winding of cut-oif relay 2 to battery. YAt armature 22| relay 204, upon energizing, completes a circuit for energizing relay 3|2 and for grounding conductor 259, at armature 222 short circuits its upper winding to render the relay slowto release and to connect direct ground to the test conductor, at armature 223 disconnects grounded conductor |53 from conductor |55 to open the circuit to the succeeding finder unit relay before the same can fully energize, atarmature 223 and working contact completes alocking circuit to its lower winding and a circuit for energizing relay H0, and at armature 224 opens the circuit to group test relay 253 to cause this relay to deenergize.

' Cut-off relay 2, upon energizing, at armatures 8 and l-andropens the circuit of line relay at armature 9 completes a locking circuit for itself to grounded test conductorY |42, and at armature I and its working Contact completes the circuit for energizing lockout relay 3. Relay H0 is energized over t'ne following circuit: Vfrom grounded conductor |53 by way of armature 223 and Working contact, armature 225, conductor |517, armature H8 and through the winding of relay ||0 to battery. At its upper armatures relay ||0 connects the line conductors of the lines in the |0-Y 'may now dialV the called subscribers number.

Lockout relay'3, upon energizing, at Yarmature `opens the original energizingrcircuit ofKvcut-O relay 2, at armatureV |2-and 'resting contact disconnects ground from the start conductor 6| to deenergize start relay 0 if no other line is calling, and at armature i2 and its Vworking contactY completesa locking circuit for itself from groundf ed armature 1. Line relay l, upon deenergizing, at armature 5 disconnects direct ground from incoming test conductor l5 at its working'contact and at its resting contact connectsrground by way of armature SEB, conductor 21|, armature 222,

conductor |42, armatures |64 and H4, and armaf ture 9 to the incoming test conductor I6 to maintain this line busy at the called end of the link. At armature 1 relay l opens the locking circuit oflock-out relay 3. Y 1

' VGroup test relay2i3,` upon,leenergizingv when its circuit is opened at armature 224, atarmature 2|9 completes a circuit for energizing relay V2527through its upper winding by way of Working contact of armature 223 and grounded conductor|53. At armature 2|1 relay 202 completes an obvious circuit for the transfer relay At 5 armature 2 I4 relay 20| prepares a locking circuit for itself, at armature `2|5 opens the original energizing circuit of line relay 201 now held energized over the calling subscribers loop, and at the working contacts of armature 2 5 connects the IN 10 start conductor 28| with the out conductor 282 so that a succeeding call may seize the next idle iinder connector link. At armature 2|6 relay 20| completes one point in the all link busy chain by connecting conductor 280 to conductor 283. 15 T he circuit for energizing relay 3|2 may be traced as follows: from grounded armature 249 and resting contact, conductor 252, armature 22|, conductor 259, armature 330 and resting contact, and through the winding of relay 3|2 to battery. 20 At armature 352 relay 3|2 prepares a locking circuit for itself, at armature 363 prepares a circuit through the lower winding of relay 3| l, which relay does not energize at this time because the lower winding is short circuited by way of arma- 25 ture 353, armature 330 and resting contact, and the normally closed spring controlled by armature 531. At armatures 354 to 351, inclusive, relay 3|2 prepares the pulsing circuit to the connector group relay. Relay 5m Vdeenergize's in case no other line is calling at this time, and at armature 5|| disconnects ground fromV the start IN lead 28|. At armature 5|3 relay 5w opens the shunt circuit of relay 535 which relay now energizes in series with relay Y523 by way of armature 52|. Relay 535, upon energizing, at armatures 53| transfers the start circuit from the beginning of the chain to the middle of the chain; at armature 532 prepares a-short circuit for relay 520 and a circuit for relay 5353, at armature 533 opens a point in the low resistance shunt of relay 530, and at armature 543V disconnects the time switch from Vrelay 550 before the time switch has had suiiicient time to energize relay 560. 45 At this point it may be advisable to consider the operation of the allotter relays in response to a second call when relay 530 is energized. In

this case start relay 5|0 is energized over the common start lead as before, and at armature 5| 50 completes the start circuitand grounds the IN start lead 28| as follows: ground by way of armature 53|, armature 5| l, resistance 515, armature 53| and working contactto IN start lead 20|', extending to the nder connector link near the 55 middle of ie chain.v At armature 5|4 relay 5|0 connects grounded armature 543 by way of armature 532 to the winding oi relays 520 and 530 with the result that relay Y52E! is short circuited and deenergizes, while relay 530 isY maintained energized over this circuit. Relay 523, upon deener gizing, at armature 522 connects springs 503 of Y the time switch TS to the winding of relay v55|).

Relay 5|3 is deenergized and ground is removed from Vthe IN start lead28l at armature 5| At 65 armature. 5M relay 5m opens the circuit of relay 530 which accordingly deenergizes. At armature 53| relay 530 transfers the start circuit back to the beginning of the chain and at armature 534 disconnects the time switch TS from the winding of relay 560.

The circuit for maintaining line relay 201 energized over the calling subscribers loop may be Y' traced as follows: from ground by way of armature 236, resting contact and armature 241, con- 7| ductor itl, armatures W3 and H3, positive line conductor t3 through the substation loop to negative line conductor iii, armatures H2 and H2, conductor 550, armature 23E and resting contact, upper left hand winding of repeating coil RC, normally closed spring controlled by armature 233, and 'through the winding of line relay 2t? to battery. Dial tone is also connected to the calling line at this time over the following circuit: from dial tone in Fig. 3, resting Contact and armature 323, tone condenser TC, conductor resting contact and armature 2136, thence over the calling loop circuit just traced. The calling subscriber, after listening to the dial tone, dials the group and line digits followed by the code selecting digit. Line relay Zell deenergizes in response to each impulse. In response to the first pulse relay at armature 230 opens the circuit of impulse repeating relay 303 which accordingly deenergizes. At armature 23H and its resting contact relay 201 closes a high resistance priming circuit for itself which may be traced as follows: from grounded conductor 232, armature 32o and working contact, conductor 253, armature riti and resting contact, conductor 25?, armature 350, resistance ZEE, conductor upper left hand winding or repeating coil RC, normally closed switch springs controlled by armature 233, and through the winding or" line relay to battery. priming circuit while sumcient to energize line relay Elli due to resistance 3&9 greatly assists the energization of line relay Eel when thesame is connected to a leaky calling line. At armature 123i and its make contact one of the multiple ground connections to relay 335 is opened but this relay, due to its slow releasing characteristics, remains energized during the impulsing period.

impulse repeating relay 3&3, upon deenergizing, at armature 32d opens a point in its own holding circuit, at armature 325 opens a further circuit to slow to release relay Stil, and at armature completes a circuit ior energizing relays 30%, 33? and The circuit for energizing relay Bue and relay extends from grounded conductor armature 323 and working contact, normally closed springs controlled by armature armature and resting Contact, and through the upper wind" ci relay 335 and the winding or relay Sill to battery. A branch or this circuit entends by way ot armature 3150 and resting contact, through the upper winding of relay 33E for energizing the latter relay. At armature relay 3355 short circuits the upper left-hand winding oi repeating coil RC in order to improve the impulsing circuit, at armature 33? completes a holding circuit for relay 3l2 by way of grounded conductor 5259 and armatures 35? and 332, at prepares an energizing circuit ior relay and the holding circuit extending to the lower windings of relays it and 33t, at armature 333 prepares a point in the circuit for the busy relay 305, and at armature 3mi disconnects grounded conductors E59 from conductors 23S and 33t.

Slow to release rela-3733i', upon energizing, at armature prepares a holding circuit for relay at rmature completes a locking circuit from grounded armature Sl through the lower windings oi relay and at armature prepares a pc in the circuit for the iirst connector relay fili. Relay due to its slow release characteri tics is maintained energized during the impulsin riod and therefore deenergizes shortly after each series of impulses.

Impulse repeating relay 300, upon energizing, at armature ifi-3 prepares a point in the energizing circuit oi relay 308 and in the holding circuit of relay armature 35@ prepares a new energizing circuit for impulse repeating relay 303 and theV circuit through the lower winding of relays 303 and 303, at armature 35i prepares a holding circuit for the lower windings of relays Sii and 3533, armature 352 disconnects ground at armature 3'55 from the even pulse conductor CSS and connects ground to the odd pulse conuctor BS-fl, and at armature 353 completes a circuit ior energizing connector group relay 4H as follows: from grounded lock conductor 21B, through armatures fill?, i532 and Q65 of the connector group relays to conductor 389, working contact and armature 30G, resting contact and armature ett, armatures tt and 353, armature and resting contact, armature 361 and working contact, conductor 3M, and through the winding oi relay iii to battery. Relay 4H at its upper armature connects the test conductors of the lines in the lil-group to the connector unit relays; at armature 30 completes a locking circuit ior itself to grounded lock conductor 218 by way ci armatures 233, 352 and 1332; and at armature prepares the circuit for relay M0.

At the termination of the i-lrst impulse line relay 20? again energizes over the subscribers loop to complete a circuit at armature 230 for energizing impulse repeating relay 303 and a circuit through the lower winding of relays 309 and 308. At armature 2st relay 25'! opens its priming circuit and recloses the circuit for slow release relay 30!! to maintain the same in energized position. The circuit for energizing relay 303 may be traced as follows: from ground at armature 350 on the energized repeating relay 309, resting Contact and armature 3M, conductor 26l, armature 23e, conductor 260, and through the winding of relay 303 to battery. A branch of this circuit extends by way of conductor 260, armatures 332, 3de and 33t, through the lower windings of relays 303 and 339 and by way of armature 35i to relay At armature tflrelay 303 again completes its holding circuit, at armature 325 again closes a multiple circuit for relay 30l, and at the normally closed spring controlled by armature 326 opens the original energizing circuit or relays ses, ser @nu ses, while at armature 32s 50 and its working contact completes a circuit from grounded conductor 233 by way of armatures 338 for energizing relay 333 and for completing a circuit by way of armature 35i through the lower windings of relays 308 and 339. Relay 309 is maintained energized over this circuit while relay 393 is energized. At armature 346 relay 308 opens a point in one of its energizing circuits, at armature till opens the original energizing circuit oi' relay 333 which is now maintained energized over its own locking circuit, at armature 3de and resting contact opens the original energizing circuit of relay 303 and at its working contact prepares a locking circuit for itself. Relays 300 and 309 at this time are maintained energized from ground by way of conductor 263, working contact and armature 325i, armature 338, armature 35i and through the lower windings of relays 3% and 333 to battery. Relay 304, upon energizing, at armature 323 disconnects dial tone and prepares a circuit for connecting ring back tone to the calling subscriber, at armature 330 and its resting contact opens the original energizing circuit of relay SI2 and at its working con-l lis tact closes a locking circuit for itself front grounded conductor 253 as wellv as opening its original energizing circuit. At this time relay 3 l2 is maintained energized over the following circuit: from grounded conductor y253, working contact and armature 331, armature 351 and resting contact, armature 332 and the winding of relay 3|2 to battery.

In response to the second pulse of the firsty series, line relay 201 again deenergizes and at ar-VV windings of relays 308 and 309, and at the normally closed springs controlled by armature Y323 completes a locking circuitV through the upper winding of relay 308 by way of armatures 333 and 348. Relay 309, upon deenergizing, at armature 350 prepares a circuit for reenerm'zing relay 303,

at armature 35| opens a further'point in the holding circuit through the lower windings of relays 308 and 309, at armature 352 connects ground at armature 318 to the even conductor 386 to complete an energizing circuit for the next connector group relay, in thiscase relay 42 I, and at armature 353 opens the original energizing circuit of relay 4| The circuit for energizing relay 42| may be traced as follows: from grounded' armature 313 and resting contact, armature 343, armature 352 andv resting contact, armature 359 and resting contact, armature 385 and working contact, conductor 386, armature 49|, and through the winding of relay 42| to battery. Relay 42|, upon energizing, at its upper armatures connects the test conductors of the lines in the 20-group` to the connector unit relays, at armature 455 opens the locking circuit of lrelay 4|| which accordingly deenergizes, at armature 46B completes a locking circuitV for itself from grounded lock conductor 218 by way of armatures, such as armature 442 and f v452, at armature 461 prepares a circuit for relay 420,'at armature 468 connects the succeeding connector group relay 43| (not shown) ,to the odd Line relay 201 reenergizcs over the calling sub-y scribers loop at the end of the second pulse, and at armature 230 closes a circuit for energizing relay 303 by way'of resting contact of armature 350 and working contact of armatureV 341, while at armature 23| the circuit to slow release relay 30| is again reclosed. Relay 303, upon energizing, at armature 324 again closes its locking circuit, at armature 325 again closes the circuit for relay 30|, and at armature 320 opens the holding circuit through the upper winding of relay 303 which accordingly deenergizes. Relay 308, upon deenergizing at armature 343 prepares a point in the original energizing circuit of relay 308, at

armature 341 opens the energizing circuit of relay 303 which is now held energized over its locking circuit, and at armature 348 opens a point in its own locking circuit and prepares a circuit for relay 309. From the foregoing it will be seen that relay 303 follows the pulses of line 201; that relays 308 and 339 are energized on the first pulse, and for each on pulse; that relays 309 and 303 are deenergized on the second pulse or on each even pulse; that relay 303 grounds the odd pulse conductor 334 on energization and grounds the even pulse conductor 383 on deenergization to successively operate the connector group relay such as relays 4| |,-42|, etc. The circuit for reoperating impulse repeating relay 303 is taken througharmatures 341 and 350 so that the circuit to relay r`303 cannot be closed until relays 308 and 309 have operated or released.

As is well known, the line relay, such as relay 201, may be sluggish in its deenergization due to the leaky or heavily loaded condition of the line connected with. In order to insure correct pulsing a so-called lock-pulse arrangement is provided. In this arrangement the armatures or springs operated by line relay 201 have a strong adjustment or tension and the springs or armatures operates by pulse repeating relay 303 also have a very stii adjustment so that this relay will veryv quickly fall back when its circuit is momentarily opened by line relay 201 at armature 230. When relay 303 is deenergized such relay cannot again energize until the repeating relays 308 or 303 have operated or released to close the circuit for relay 303, even though the line relay is immediately reoperated. Relays 308 and 309 need not necessarily be fast operating relays in order to repeat the impulses received. In addition a priming circuit or artificial leak is provided through resting contacts on the line relay 201 for facilitating its reoperation over long, clear lines. This impulsing circuit in combination with the odd and even pulsing circuits has proven to be a very satisfactory circuit arrangement on lines of varying electrical characteristics which hereto- Vfore have prevented automatic working.

In responseV to the third pulse relays 201 and 303 deenergize and relay 303 causes the energization of relay 309 as previously described for the first pulse. When relay 303 grounds the odd conductor 384 the third connector group relay 43| (not shown) is energized over the odd pulse conductor 384 at armature 458. In the same manner as described for relay 42|, relay 43| (not shown) closes its upper armatures to connect the test leads of the 30-line group; opens the locking circuit of relay 42| which deenergizes; closes its own locking circuit; prepares the circuit through its associated line connecting relay (not shown) similar to relay 420; and connects the connector group test relay of the 40-line group (not shown) to the even conductor 380. At the end of the third pulse relays 201, 303 and 308 energize as previously described for the end of the rst pulse. Y

In` response to the fourth impulse relays 201, 303 and 309 deenergize as described for the second pulse. When relay 309 grounds the even conductor 333 the connector group test relay (not shown)Y for the 40-line group is energized in a manner similar to that previously described. This connector group relay closes the test leads of the 40-line group; opens the locking circuit of the connector group relay of the 30-line group which deenergizes; closes its own locking circuit; prepares a circuit through its own associated line connecting relay (not shown), and connects the connector group test relay of the ith line group (not shown) to the odd conductor 384.

In the sarne manner as just described, each odd pulse grounds the odd conductor 384 to energize the corresponding connector group relay, and each even pulse grounds the even conductor 383 to energize the corresponding connector group test relay. The connector group test relays 413i to @3i and the associated connector group line connecting relays i533 to dii@ are not shown because their circuit operations are identical with the connector group relays shown. In response to the seventh pulse odd conductor 38e is grounded by relay 329 to energize the connector group test relay iii of the "iiiline group by Way or armature 258 on the connector group test relay of the Sil-line group. Relay i'ii at its upper armatures connects the test leads of the lines in the iii-group to the connector unit relays, at armature 252 opens the lockingy circuit of the last operated connector group test relay, at armature 453 closes its own locking circuit, at armature 255i connects the connector group test relay 28! oi" the Sil-line group to even conductor 333, at armature 1355 prepares the circuit to line connecting relay siii of the 'iiiline group, and at armature 256 prepares a circuit for the ring reversing relay 3 lli.

Relays 20'? and 363 remain energized after the last impulse of the series and after an interval siovv to release relay 391 deenergizes. At arrnan ture 343 relay 3S? opens a point in the pulsing circuit as well as the holding circuit of relay 323 which accordingly deenergizes, and at armature 325 opens a point in the original energizing circuit of relay til. Relay 336, upon deenergizing, at armature 33S removes the short circuit from the repeating coil RC, at armature 331 opens the locking circuit of relay 322' and substitutes the circuit through the lower Winding of reay 3H in series with the Winding of relay 3i?, whereby relay 3i2 is maintained energized and relay 3H is energized over the circuit from grounded conductor 259 in series with the Windof relay 3 i 2. At armature 33 relay 335 opens the circuit to relays 328 and 339 to deenergize the same if they should be energized at this time, at armature 339 opens a point in the circuit to the busy relay 355, and at armature 3432 reconnects grounded conductor 25S to conductors 339 and 392. Relay 3i i, upon energizing series with relay 352, at armature 35i prepares a locking circuit for itself, at armatures 358 and 35S prepares the pulsing circuit over the odd and even conductors 383 and 385 to the connector unit relays and at armatures 363 and 33 prepares a circuit for connecting the grounded lock conductor 2li) to conductor 338.

The cailing subscriber may now dial the second digit of the desired called subscribers number. in the same manner as previously described, line relay 2S? and repeating relay 393 deenergize for each impulse and in response to the iirst impulse completes the circuit for energizing relays 365, and 3%. Relay 306, upon energizing, at armature 33'!! opens the holding circuit of relay to cause this relay to deenergize and like- *Ivise completes a locking circuit through the upper winding of relay il for maintaining this relay in energized position. in response to the 'energization of relays 35i and 329 a circuit is completed for energizing the iirst connector unit relay liti. Relay Si?, upon deenergizing at armatures 364 to 361 prepares the pulsing circuit for the code selecting relay CSR.

Relay Gili energizes over the following circuit: from grounded lock conductor Eis, armatures 4 l2, M5, 432 and similar armatures on the connector unit relays (not shown), conductor 33's', working contact and armature 366, armatures 345 and 353, armature 35| and Working contact, conductor 396, and through the winding of relay del to battery. At armatures 292 and A83 relay 40E connects the talking conductors 252 and 255 of the link tothe connector group relays, at armature i394 connects the test conductor 382 to the test conductor 3ft of line li; at armature 435 completes a locking circuit for itself from grounded lock conductor 278 through the armatures of the unoperated connector unit relays, at armatures 36 prepares a circuit to the succeeding even connector unit relay G82, at armature 431 prepares a point in the circuit for the trunk switch-through relay 2 I3, and at armature 33S grounds conductor 392. Line relay 29'! energizes at the end of each pulse and again completes the circuit for energizing repeating relay 3D3 in case relays 308 and 339 have operated or released, as previously described.

In order to describe the operation of the connector unit relays it will be assumed that the second digit being dialled is more than the digit I. Relays 23'?, 333 and 399 deenergize in the same manner as previously described for the second puise. At armature 353 relay 359 opens the circuit to connector unit relay 46|, now held over its locking circuit, and at armature 352 disconnects ground from the odd pulse conducto-r 383 and connects ground to the even pulse conductor 385 to energize the second connector unit relay M12. This circuit be traced as follows:

ground by way of armature 416 and resting conu tact, armature 343, armature 352 and resting contact, armature 35S and working contact, even pulse conductor 385, armature 35 and through the Winding of relay 402 to battery. At its two uppermost armatures relay 22 connects the link line conductors 252 and 255 to the contacts of 425 the connector group relays, at the third uppermost contact connects the link test conductor 332 to the test conductor of line 'i2 by Way of the operated contacts on connector group relay lill.

ductor 228 by Way of armatures H2 and dit and similar armatures on other connector unit delays (not shown); at armature 532 opens the locking circuit of relay 46E which now deenergizes and at armature 1234 connects the third connector unit relay M13 (notshown) to the odd pulse conductor 383. At the end of the second pulse relays 29! At armature 1833 relay H92 completes a lockving circuit oreitself from grounded locking conand 333 reenergizes and relays 333 deenergize, as

previously described.

ln response to the third pulse relays 29! and 383 deenergize and relay 329 reenergizes to ground the odd pulse conductor 383, as previously described. The third connector unit relay 353 (not shown) is energized to connect up the 6 Yin response to succeeding pulses to connect the test conductors of the succeeding lines in the group to the link test conductor 382. Since, in this case subscriber S4 on line 1| is being called,

Vthe secondY digit therefcrecomprises only one pulse and therefore the rst connector unit relay 49| is energized to connect the test conductor 34 of line 1| to the link test conductor 362.

After the last impulse of the second digit relays 261 and 393 remain energized and relay 391 falls back after an interval. At armature 343 relay 301 opens the locking' circuit of relay 306 which thereupon deenergizes. Relay 396, upon deenergizing, at armature 331 opens the locking circuit of relay 3|| which'likewise deenergizes; at armature 336 opens the circuit extending through the lower windings of relaysV 306 and 369 to deenergize the same if they are energized; and at armature 349 grounds conductors 269 and 394. Relay 3| I, upon deenergizing, at armature 351 opens a point in its own locking circuit, and atarmatures 358, 359, 369 and 36| prepares the impulsing circuit to the code selecting relays CSR shown in Fig. 6.

The calling subscriber now dials the third or code selecting digitfof the desired called subscribers line. Line relay 201 follows the impulses transmitted by the calling subscriber again causing relay 303 to deenergize for each pulse. Relays 306, 301 and 309 energize in the same manner 'as previously described. At armature 339 relay Y 306 prepares the circuit for busy relay 365. At armature 343 relay 301 completes the lockingfcircuit for relay 395, and at armature 345 prepares' the circuit for relay 6|0. At armature 352 relay 369 grounds the'odd pulse conductor 398 in response tothe first pulse and at armature 353 completes an energizing circuit for relay 6|6. This circuit may be traced as follows: from grounded armature 323, conductor 218, armature 24|, conductor 219, armatures 652, 632 and 622, conductor 395, resting contact and armatures 361 and 36|, armatures 353 and 345, armatures 350 and 366 and their resting contacts, conductor 399, and through the winding of relay 6|6 to battery.

The first code selecting relay 6|0 energizes over the above traced circuit, and at armature 6|| closes theY circuit for energizing the busy test relay 305 in its rst step in series with test relay 3|5 in case the called line is busy. At armature 6|3 relay 6|0 completes a locking circuit for itself through the armatures 622, 632, 642 and 652 to the grounded lock conductor 219, at

armature 6|4Y connects the second code selecting,

relay 629 to the even pulse conductor 391and at armatures 625 and6|6 prepares points in the code ringing circuit. At the end of the first pulse relays 291, 303 and 398 energize as befcre.V

In response to the second pulse relays 291, 393 and 309 deenergize, as previously described. At armature 353 relay 339 opens the original energizing circuit of relay 6|El, which is now held energized overY its locking circuit, and at armature 352 grounds the even pulse conductor 391 to energize relay 620. This circuit may be traced as follows: from ground by way of armature 316 and resting contact, armature 343, armature 352 and resting contact, armatures 359 and 365 and their resting contacts, conductor 391, armature 6M, and through the winding of relay 620 to battery. At armature 62| relay 629 connects the test relay 3|5 in series with the busy relay 305 to test the idle 0r busy condition of the called line, at armature1622 opens the locking circuit of relay 6|0 which now deenergizes, at armature 623 closes its own locking circuit to grounded lock conductor 219, at armature 624 connects the thirdY code selecting relay 630 to the odd pulse conductor393, and at armatures 625 and 626 prepares points in the code ringing circuit.

Code selecting relays 639, 640 and 650 energize in response to the third, fourth and fifth impulses as a result of relay 399 alternately grounding the odd and even pulse conductors 398 and 391. Each subsequently operated code selecting relay opens the locking circuit to the previously operated code selecting relay to cause its deenergization. In response to the sixth pulse relay 650 energizes over the even pulse conductor 391. At armature 66| relay 660 again completes the busy test circuit, at armature 663 locks itself to grounded lock conductor 219, at armature 664 opens its original energizing circuit after completion of its locking circuit, at armature 665 switches from onev set of code ringing contacts to the other set, and at armature 666 completes the circuit for energizing the ring reversing relay 3|4. This circuit may be traced as follows: from ground by way of armatures 456 and 439, conductors 392, armature 666, con- Y ductor 319, and through the winding of relay 3|4 to battery. At armatures 31| and 312 relay 3|!! reverses the ringing connection so that generator will now be connected with the positive line conductor instead of the negative line conductor.

Vselecting `relay 650 to cause its deenergization.

In response to the eighth, ninth and tenth pulses code selecting relays 620, 639 andv 640, respectively, energize and lock, and deenergize the previously energized code selecting relay in the same manner as previously described. From the foregoing it will be seen that code selecting relays Bl, 629, 630, 649, and 650 are energized in response to the first five impulses in the code selecting digit, that relays 650 and 660 are energized for the sixth pulse, that relays 6|0 and 669, relays 620 and 660, relays 630 and 660 and relays 640 and 660 are energized for the seventh,

' eighth, ninth and tenth pulses.

In case the called line is busy a circuit is com- Ypleted for energizing the busy test relay 305 in its rst step in series with the marginal test relay 3|5 as follows: from ground on the test conductor 34 of the called line, armatures 313 and 393, conductor 392, through the upper winding of marginal test relay 3|5, conductor 38|,

Vthrough the operated one of the multiple contacts 61| to 66|, inclusive, conductor 394, resistance 33 l, armature 339 and through the winding of busy test relay 305 to battery. Busy relay 355, due to resistance 34| closes only its X contact at armature 334 to prepare a circuit for fully energizing itself when relay 306 later on deenergizes. After the last pulse of the code selecting digit relays 231 and 333 again energize, and relays 336, 301, 303 and 309 deenergize, as previously described. Relay 306, upon deenergizing, at armature 339 completes the circuit for fully energizing the busy test relay 305 as follows: from grounded conductor 259, armature 334 and working contact, normally closed springs controlled by armature 333 and through the winding of busy relay 305 to battery.

Assuming, however, that the called line is idle, then busy relay 305 is not energized because no ground is connected to the test conductor 34 of the called line. Now, when relay 306 deenergizes after the code selecting digit a circuit is completed for energizing the test relay 3|5 in series with the cut-off relay 22 of the called line as follows: from grounded conductor 259 armature 333 and resting Contact on the unoperated busy relay 355, armature 330, conductor 394, through the operated one of t1 e armatures 6H to 66|, inclusive, conductor 33|, through the upper winding of test relay 3|5, conductor 382, armatures 433 and 51d, conductor 34, armature 25 and resting contact, and through the winding of cuto relay 22 to battery. At armature 311 relay 315 completes its own locking circuit before operating its remaining armatures as follows: from ground at the normally closed springs controlled by armature 228, conductor 215, armature 322, conductor |53, armature 311, and through the lower Winding oi test relay 3|5 to battery. At armature 313 relay 3|5 prepares a circuit for connecting ground to the negative link conductor 252 since ring reversing relay 3|4 is energized, at armature 314 prepares the circuit for connecting generator to the positive link oonductor 255, at armature 315 connects direct ground to conductor 382 to maintain the called line busy; at armature 316 grounds conductor 253 to energize the prepared connector group relay, in this case relay 110, and at armature 318 prepares the circuit for energizing the pick-up relay 610.

The circuit for energizing connector group relay li@ may be traced as follows: from grounded armature 316 and working contact, conductor 2633, armature 155 on the operated connector group relay 511, and through the winding of relay !10 to battery. At armatures 412 and 413 relay d10 connects the line conductors 32 and 33 of the called line to the link conductors 252 and 255. 'When cut-off relay 22 energizes in series with relay 315 that relay at armatures 21 and disconnects the line relay 2| from the line conductor 32 and ground, at armature 23 connects the grounded test conductor 34 to the nder test conductor 35 to mark this line as busy in the finder end of the link, and at armature 29 completes an obvious circuit for energizing the lockout reiay 23. Relay at armature 3| opens point in the start circuit to start conductor 61.

At the beginning of each code ringing cycle generated by the ringing machine (not shown) the ringing machine grounds the pick-up lead and completes the circuit for energizing relay 610 as follows: from grounded pick-up lead extending from the ringing machine, normally closed springs controlled by armature 612, conductor 380,

armature 318, conductor 216, armature 240, conductor 211, and through the winding of pick-up relay 610 to battery. At armature 61| relay 610 prepares a circuit for ringing relay 3|3, at armature 612 opens its original energizing circuit and 5 completes its locking circuit to lock conductor 210, and at armatures 613 and 614 prepares further points in the circuit to ringing relay 3|3.

The ringing machine is arranged to ground the code ring conductors at certain prede- 10 termined times during its cycles ofV operations, as indicated at the lower left-hand corner of Fig. 6. For example, 4-4 indicates that this conductor is grounded at predetermined periods in each cycle to operate the ringing relay 3|3 to-15 generate four sho-rt rings, then a pause, followed by four more short rings. In this case, assuming that the code ring conductor 2--2 has been selected, then ringing ,relay 3|3 is energized over the following circuit: from ground at the ringing 20 machine over the conductor marked 2 2, resting contact and armature 66|, armatures 645 and 613, working contact and armature 665, conductor 680, armature 61 I, conductor 399, and through the winding of ringing relay 3 I3 to battery. The 25 code ring conductor 2--2 was selected because in this case it is assumed that the code selecting digit dialled was the digit 0, in which case code selecting relays 640 and 660 have been operated and locked in operated position. Each time ringing 30 relay 3|3 is energized from the ringing machine, said relay at armature 368 connects ground by way of armatures 31| and 313 to the negative link conductor 252 since relay 3|4 is energized, at armature 369 connects generator to the posi- 35 tive link conductor 255 by way of armatures 312 and 315 to code ring the called subscriberx and at armature 310 completes an obvious circuit for energizing co-ndenser discharging relay 3|0. Relay 3|0 follows the impulses transmitted by 40 ringing relay 3|3, but due to its slow release characteristics this relay lags behind ringing relay 3|3 and at armature 354 connects battery through resistance 355 to the negative link conductor 352 momentarily after each application oi 45 generator in order to discharge the condensers associated with the ringers on the called line. At armature 356 relay 3|0 completes a circuit for transmitting ring back tone to the calling subscriber as follows: from generator through work- 50 ing contact and armature 356, working contact and armature 328, the tone condenser TC to conductor 254 and thence over the calling subscribers loop, as previously described.

Ringing current to the called subscriber may 55 now be traced as follows: from generator, working contact and armature 312, working contact and armature 369, armature 314, positive link conductor 255, armatures 493 and 413, conducto-r 33, through the ringers connected to the positive 60 line conductor of this line to ground. In case the ringers of this line should be bridged instead of grounded, then the ground return circuit extends back by way of negative line conductor 32, armatures 412 and 492, conductor 252', arma- 65 tures 313, 368 and 31| to ground.

When subscriber S4 answers his code ring during the` silent period or when ringing relay 3|3 is in deenergized position back bridge relays 2|| and 2|2 energize in case the called line is a me- 70 tallic line, or in case the called line is a grounded line then relay 2|| alone is energized. The circuit for energizing back bridge relays 2| and 2|2 in case of a metallic line may be traced as follows: from ground through the winding of 75v relay 2|2, lower right-hand winding of repeating coil RC, conductor 255, resting contact and armature 359, armature 314, over the circuit to the called subscribers loop previouslytraced for ringing current, back to conductor 252, armatures 313 and 358,' conductor 253, through the upper righ*- hand winding of repeating coil RC over armatures 238 and 321 in multiple, through the winding of relay 2|| to battery. yIn case the called line is a grounded line relay 2 |2 is short circuited over the following path: from the grounded positive line conductor ofthe called line over armatures Z13 and 433, conductor 255, armatures 314 and 359, conductor 256, through the right-hand winding' of repeating coil RC, and through the winding of relay 2 |2 to ground.

Relay 2|I, upon energizing, at armature 242 and resting contact opens a point in the circuit to disconnect relay 200 and at its working contact completes a circuit for energizing relay 2|0. At armature 203 relay 2|| completes a circuit for energizing the battery reversing relay 209 in case the calling line is such as to require reverse battery supervision. The circuit for energizing relay 2|0 may be traced as follows: from ground at ,armature 32|, conductor 255, armature 242 and working contact, normally closed springs controlled` by armature 231, and .through the winding or" relay 2|0 to battery. At armature 231 relay 2li) completes its own locking circuit to grounded conductor 259 and opens its original energizing circuit, at armature 238 completes the talking circuit, at armature 233` removes the short circuit from around relay 208 to permit its energization in case the calling line is a metallic line, at armature 239 opens one of the multiple circuits to relay 302, at armature 240 opens the circuit to pick-up relay Y519 which accordingly deenergizes and at armature 24| disconnects ground from lock conductor 219 to cause the deenergization of the operated code selecting relays.

Relay 208 now operates in series withthe calling Y subscribers loop and relay 201 in case the calling line is a metallic line as follows: from ground through the winding of relay 200, normally closed springs controlledV by armature 234, lower lefthand winding of repeating coil RC, resting contact and armature 249, conductor |5|, armatures |13 and |i3, positive line conductor |5 of line |1 and thence through the calling subscribers loop and over the previously traced circuit through the winding oi line relay 201 to battery. In case the calling line is a1 grounded line then the positive line conductor such as conductor I5 will be grounded and relay 203 is prevented from operating. Relay208, uponenergizing, if the calling line is a metallic line, at armature 232 completes a circuit for energizing battery reversing relay 209 in case the calling line is in a group requiring kreverse battery supervision, in which case conductor |58 is connected to contacts, such as contactsV |8, to conductor |51 which is Vgrounded thereby completing the circuit by way of arrna-r ture 243 for energizing the battery reversing Yrelay 209.

All the code selecting relays in Fig. 6 now restore and relay 550 at armature 056 opens the circuit to ring reversing relay 3|4 and relay 519 at armature 61| opens the circuit to ringing relay 353. Relay 209, upon energizing, at arma-V tures 233 and 234 reverse battery to the calling line, and at armature 235 completes a locking circuit for itself independent of armature 232.

When the calling line is a metallic line, talking battery is supplied from the windings of yrelays 201 and 208 through theleit-hand windings of the repeating coil RC over the resting contacts and armatures 246A and 241 to conductors |50 and |5|, and thence over the calling loop. In case the calling line is a grounded line, then 5 talking battery is supplied through the winding of line relay 201 and from the grounded positive line conductor of the calling line. When the called line is a metallic line talking battery is supplied through the windings of relays 2|| 10 and 2| 2 over the previously traced circuit to the called subscribers loop and in this case if relay 2|0 is operated the circuit for relay 2|| extends from the winding of repeating coil through armature 321 and conductor 266. In 15 case the called line is a grounded linethen the battery is supplied through the winding of relay 2|| andfrom ground on the grounded positive line conductor of the called line.

After conversation and responsive to the called 20 party replacing his receiver, relays 2|| and 2|2 deenergize. At armature 243 relay 2|| opens the circuit of relay 209 in case it is energized, and at armature 242 prepares the circuit for the disconnect relay 205 so that this link will be 25 automatically released after a predetermined interval if the calling subscriber fails to replace his receiver. Battery reversing relay 209, if energized, now deenergizes and reverses battery tothe calling line for supervisory purposes. response to the calling subscriber replacing his receiver, line relay 201 deenergizes and likewise relay 208, if energized. At armature 230 line relay 201 opens the circuit of relay 303 which deenergizes and at armature 23| opens one of 35 the multiple ground circuits to slow to release relay 30|. Relay 303, upon'deenergizing, at armature 325 opens the circuity of slow to release relay 30|, at armature 321 disconnects relay 2|| from conductor 253 and at armature 325 closes 40 the circuit for relays 306, 301 and 309. Relay 30|, upon deenergizing, at armature 3|8 opens the circuit of relay 302 and disconnects ground from test conductor |52 to open the circuit of the cut-off relay 2. Cut-01T relay 2, upon de- 45 energizing, at armature |0 opens the circuit of lock-out relay 3, and at armatures 8 and |0 operatively connects the line relay to the calling line. After an interval lock-out relay 3 deenergizes and at armature I2 prepares the circuit for 50 start lead 6|.

Slow to release relay 302, upon deenergizing, at armature 320 disconnects ground from relays 300, 301 and 309 to cause their deenergization,

at armature 32| disconnects ground from con- 55v ductor 265 to open a point in the circuit of the disconnect relay 206,Y at armature 322 opens the locking circuit of relay 3|5 and disconnects ground from conductors |53 and |51 to unlock the operated finder group relays ||0 and the 60 operated finder unit relay |01, and relays 204 and 202. At armature 323 relay 302 'disconnects ground from the lock conductor 218 to unlock the operated connector unit relay 40| and connector group relay 41|. Relay 40|, upon de- 65 energizing, at armatures 492, 493 and 494, disconnects the conductors of line 1| from the control relays in the link. Relay 41|, upon deenergizing, at armature 415 disconnects the test lead 30 from the link circuit thereby opening the cir- 70 cuit to cut-off relay 22. At armature 455 relay 41| opens the circuit to relay 410 which accord- Y ingly deenergizes and disconnects the" line conductors 32 and' 33 from the link. Relay 3| 5, upon deenergizing, at armature 315 disconnects 75 ground from test conductor 2%, at armature 316 disconnects ground from conductor 368 tov open the circuit of relay fl'l, and at armatures 3T3 and Sid opens a point in the talking circuit. Relay 291i, upon deenergizing, at armature 222i opens the locking circuit from relays Ztli and 3M to cause the latter relays to deenergize.

Relay ll, upon deenergizing, at armatures H2 and E33, disconnects the line conductors I4 and l5 from the repeating coil RC. Relay Il l, upon deenergizing, at armature lll disconnects the test lead of the line from test conductor |52. Relay lill, upon deenergizing, at armatures H2, H3 and i'lll, disconnects the control relays of the link from the calling line. Relay 2532, upon deenergizing, at armature 2l? transfers the transfer relay 2li! from direct ground to the IN lead 28! of the start chain so that if the 1N lead 233 is grounded at this time the transfer relay 20E will not restore and interfere with the operation of a succeeding link. In case the in lead 225 is not grounded 259i deenergizes and at armature 2 l opens a point in the all link busy chain. At armature 2l5 relay 2l!! disconnects the out lead S52 and connects up the in lead 28! to line relay 2%?. Relay am, upon deenergizing, at armature 233 short circuits relay 2% and grounds conductor ll, at armature 3'? opens a point in its own locking circuit as well as preparing its own original energizing circuit, and at armature 233 separates the right-hand windings of repeating coil RC. Relay 394, upon deenergizing, at armature 328 restores the circuit for connecting dial tone to a calling line, and at armature prepares a point in the circuit to relay alii as well as a point in its own original energizing circuit. Cut-off relay 22, upon dec-energizing, at armatures 2'! and 28 prepares the circuit for line relay 2l and at armature 29 opens the circuit to lock-out relay 23. Lock-out relay 23 restores and at armature 3l prepares the circuit to start lead 5l. All relays are now in their normal position and the link circuit may be used in a subsequent call.

Assuming now that the called line was busy instead of idle, and returning to the operation at a time when busy relay 2li?) was fully energized after the code selecting digit was dialled, busy relay 365, upon energizing, at armature 33! connects the busy tone to the calling line as follows: frein busy tene by way of armature 33t, resting Contact and armature 35%, working contact and armature tone condenser TC, conductor 25d, resting contact and armature 2li?, and thence over the calling subscribers loop, as previously described. At armature 332 relay 3F35 prepares a circuit for grounding test lead 3%2, and at arrnature 333 opens the circuit to relays 398, Sill and and likewise prepares a circuit for reoperating relay in case relay Eil? is again` operated.

t armature relay 385 prepares a point in the circuit to reverting call relay 255 and at armature 335i completes a locking circuit for itself as follows: from grounded locking conductor armature 335i and working Contact, normally closed springs controlled by armature 331i, and through the winding of busy relay 365 to battery. After receipt of busy tone the calling subscriber replaces his receiver, thereby opening the circuit to line relay 263i, which accordingly deenergizes and causes the release of the operated relays in the manner as described for the release 0f an idle line. In this case, since busy relay 395 is energized, the deenergizatien or relay at armature 22! opens the circuit of busy relay 3&5 to cause its deenergization.

The foregoing circuit descriptions are the circuit operations for ringing the subscribers, such as subscribers S4 and Sil, which have their ringers connected to the positive line conductor. As diagramniatically illustrated in Fig. e line ll has ten substations connected thereto, live of such sub-stations having their ringers connected to the negative line conductor and the remaining lines having their ringers connected to the positive line conductor. In order to ring the sub scribers having their ringers connected to the positive line conductor, the code ringing digit dialled is six or more so that the code selecting relay S6!! will be energized to cause the energization of ring reversing relay SI15, as previously described. In order to ring the subscribers having their ringers connected to the negative line conductor the code ringing digit dialled is less than six, and therefore relays E69 and 3M are not energized. In this case the operation of ringing relay 3|3 connects generator to the negative line conductor to operate the ringers thereon. This arrangement is known as ten party divided ringlng. l

Some of the party lines have as many as twenty subscribers on a line, for example, the line Nos. 2G and 2l' shown in Fig. 4, illustrates a grounded line having twenty subscribers thereon. As will be noticed armatures 52d and i3d on connector group relay 42| are tied together and connected to the test conductor [le of this line. Arrnatures 422 and 62T and armatures 523 and Q28 are tied together and connected respectively to the negative and positive line conductors il? and 43. From the Vforegoing description it will be therefore understood that this line may be connected with in response to dialling the digits or 2- The rst ten subscribers on this line are signalled by dialling digits 2 and 5 and then a code selecting digit 1 to 0. In response to the .calling subscriber dialling the digits 2 and 6 the control relays operate in the saine rnanner as previously described to cause the energization of the connector unit and connector group relays ll2l and 466. In response to dialling the code selecting relays CRS are energized as previously described to select the desired code. Since in this case ring reversing relay 3M is not energized, ringing relay 3l3 always connects the generator to the negative line and since relay 600 is not energized, the code selected by the code digit dialled is determined by the conductor selected over the resting contacts of armatures of relay 693B. The second ten subscribers on this line are signalled by dialling the digits 2 and 7 and then a code selecting digit 1 to 0. In response to the calling subscriber `dialling the digits 2 and '7l the control relays operate as previously described to cause the energization of the connector unit and connector group relays 42i and dill. When relay lill operates its armature did a circuit is cornpleted for energizing the code switching relay till-ll, as follows: from grounded conductor 2249, armatures 69 and dill, conductor 3%, and through the winding of code switching relay iilil to battery. Relay Stil at its resting contact disconnects the first ten code ring conductors and at the working Contact of these armate es conn nects the second ten code ring conductors. In response to dialling the code selecting digit the code selecting relays are operated as before to select the desired code ring conductor in the second set. VNow, when the ringing relay 3I3 is energized over the selected code ring conductor, generator is connected to the negative line conductor in accordance with the selected code ring conductor.V The following chart shows the digits -dialled and the code ring conductors selectedin accordance therewith.

ZU-paty code ring Digits Ring cond. Digits Ring cond.

1 27-1 2-3 2 27-2 2-4 3 27-3 3--1 4 27-4 3-2 1-1 27-5 3-'3 1-2 27-6 3-4 1-3 27-7 4f-1 1-4 27-8 if-2 2-1 27-9 4-3 2-2 27--0 4 4 scriber S I.

Revcrting calls In order to describe a reverting call it Will be assumed that substation S desires to call another subscriber onV his own line, for example subscriber #1. Subscriber S therefore removes'his receiver and dials the line selecting digits 1 and 7 and then the code selecting digit assigned to sub- The finder group relays H0 and and the finder unit relay |91 operate to ccnnect the control relays ofthe link to line I1. The connector group relay 4I I, the connector unit relay 401 and the code selecting'relays in Fig. 6 operate also in the same manner as previously described. Since the called subscriber, subscriber S I, is on the same line as the calling subscriber S, line i1 is marked busy and busy relay 335 energizes in the same manner as previously described to transmit the busy tone to the calling subscriber. In response to the receipt of busy tone subscriber S now replaces his receiver thereby opening the circuit of line relay 201 which accordingly deenergizes. At armature 239 relay 251 opens the circuit of relay 333. Relay 333, upon deenergizing, at armature 325 opens the circuit of relay 33| and at armature 324 grounds the test conductor 352 to maintain the line busy and to hold the cut-o relay 2 and slow release relay 302 in energized position as follows: from grounded'armature and resting Contact, armature 332, conductor 332, armature 418, armature 491, test conductor I6 of line |1, armature 6 and resting contact, one branch eX- tending to the Winding of relay 2' to hold said relay .and the other branch extending by way of armature 9, armatures I I4 and |14, conductor |52, armature 222, armature 239, conductor 212, and through.` the winding of relay 352 to battery for holdingrthe latter relay.

Slowrto release relay 35|, upon deenergizing, at armature 3|8 and working contact, opens the original energizing circuit of relay 362 now maintained energized over the previously traced circuit, and the resting contact ofA armature 3 I B completes a circuit for energizing reverting call relay 255. This circuit may be traced as follows: from ground at the resting contact of armature 324 over the previously traced circuit for holding cut-off relay 2 and relay 392 Venergized to conductor |52, conductor 21|, armature BIB and resting contact, armature V335, conductor 213 and through the Winding of reverting call relay 205 to battery. At armature 225 relay 255 opens the circuit to nder group relay I i0 which deenergizes, at armature 226 opens one of the multiple circuits to relay 302, and at armature 221 completes a circuit` 'ringing relay 3 I3.

rCurrent to line I1.

for energizing test relay 3|5 as follows: from ground at the normally closed springs controlled by armature 228, conductor 215, armature 322, conductor |53, armature 221, conductor 214, and

through the lower winding of relay 3 I 5 to battery. 5

Relay ||0, upon .deenergizing at armatures II2v and I| 3 disconnects the line conductors I4 and Y I5 from the link conductors |50 and I5I thereby opening the circuit to line relay 201.

At armature 311 relay `3I5 completes a locking circuit for 10 itself, at armature 318 prepares a circuit for energizing pick-up relay 610, at armatures 316 completes the circuit for energizing relay 4 I 0, at arma ture 315 grounds the test lead 392 to maintain this line busy, and at armatures 313 and 314 prepares points in the ringing circuit. The circuit for energizing relay 4|0 may be traced as follows: from'grounded armature 316 and Working contact, conductor 268, armature 492 and through the Winding of relay 4I0 Vto battery. At armatures 20 495 and. 496 relay 4I0 connects the line conductors I4 and I5 to the link conductors 252 and 255. At the beginning of the code ringing cycle the pick-up conductor is grounded in the ringing machine to cause the energization of pick-up relay 25 610 as previously described. At armature 612 pick-up relay 610 completes its own locking circuit, and at armature 61| prepares the circuit for When the selected code ring conductor is grounded by the ringing machine, ringing relay 3|3 is energized over the previously traced circuit in accordance withA the number or" times the code ringing conductor is grounded by the ringing machine in order to transmit ringing traced as follows: from generator, resting contact of armature 31|, working contact, and armature 368, armature 313, conductor 252, armatures 415 and 495 to negative line conductor I4 of line II and thence through the ringers on line I8 to 40 positive line conductor I5, armatures 495 and 491, conductor 255, armature 314, armature 359 and Working contact, and armature 312 and resting Contact to ground.

Y At completion of the code ring and in response to either the calling or called subscriber answering during the silent period relay 2|I energizes in series with relay 2|2 over the following circuit: from ground through the winding of relay 2|2, lower right-hand Winding of repeating coil 50 RC, conductor 253, resting contact and armature 369, and thence over the previously traced ringing circuit through the substation loop, back to armature 398 and resting contact, conductor 253, upper right-hand winding of repeating coil 55 RC, armature 238 andV resting contact, and

armature 242 relay 2|| completes the circuit for energizing relay 2 IB and opens a point'in the circuit to the disconnect relay 235. Relay 2I0, upon 60 energizing, at armature 231 closes itsown locking circuit and opens its original energizing circuit, at armature 23B removes the short circuit from around relay 208, at armature 24| disconnects ground from conductor 219 to deenergize the code 65 selecting relays, at armature 238 opens the circuit to relays 2|! and 2|2 which accordingly deenergize, and at armature 239 opens the circuit to relay 302 to cause its deenergization. After an interval slow to release relay 302 deenergizes 70 and at armature 323 opens the locking circuit of relays 451 and 4|I; and at armature 322 opens the circuit to relays 3I5, |II, |01, 204, and 202. Relay 401,'upon deenergizing, at armatures 415, 415 and 418 disconnects the link conductors 252, 75

The ringing circuit may be 35 255 and from line il. Relay 2| I, upon deenergizing, opens at armature 227 the circuit to test conductor i3 and at armature 1332 opens the circuit of relay dit which accordingly deenergizes. Relay 3MB, upon deenergizing, at armatures 3'I3 and '3l-3- opens further points in the talking and ringing circuits, at armature 355 disconnects ground from test conductor 332, at armature Zilli disconnects ground from conductor 268, at armature 3l? opens a. point in its locking circuit, and at armature 373 opens a point in the original energizing circuit of pick-up relay 613. Relay l I i, upon deenergizing, at armature I I8 opens the circuit to relay I i i) which accordingly deenergizes, and at armature l iii disconnects the test lead of line il from the link. Relay Iil'l, upon deenergizing, at armatures H2, |23 and Il'l opens further points in the link circuit. Relay 236, upon deenergizing, at armature 225 opens the locking circuit oi relays 2m, 322 and 325. Relay 232, upon deenergizing, at armature 2i? transfers relay 2M from direct ground to the in start lead 2M. Reverting call relay 285, upon deenergizing,

qmature 221 opens a point in the original energia -g circuit of relay 3 I 5.

Cutoff relay 2, upon deenergizing, at armature lil opens the circuit oi lockout relay 3, and at armatures 8 and It! reconnects line relay to the conductors or" line Il. Line relay I now energizes over the subscribers loop as follows: ground by way of armature Il! and resting contact, lower winding of line relay I, conductor I5, the substation loop conductor I3, armature 8, and through the upper winding of relay l to battery. At armature G line relay I grounds the test conductor to busy this line in the connector end of the link circuit, and at armature 1 completes the locking circuit ior lock-out relay 3. Lock-out relay 3 is maintained energized to prevent grounding ci the start lead 6l. Relays 365, 2||J and now dcenergize. Relay Ztl deenergizes in case the in lead 23E is not grounded as previously described. The entire link is now released and talking battery is furnished through line relay i to the subscribers on line I7. After conversation and in response to both parties replactheir receivers line relay I restores and opens the circuit of lool -out relay 3 which is likewise deenergized and restoresthe line circuit to normal.

Coll to switch-through, trunk It will now be assumed that subscriber S deand in order to do so dials the digits 8 to connect with the trunk line extending to items-...s exchange. in response to subs1- noving his receiver and dialling the the finder relays, the control relays, and conrector relays are operated as previo ess: :ed to complete a connection with t ed trunk line. In this case, since the digpulsing period. This circuit may be traced as follows: from grounded test conductor dill, armatures 433 and 393, conductor 332, armatures 437| and 425, conductor 273, upper winding of switch through relay 2I3, conductor 233, armature 3H, 5v

resistance 34|, armature 339, and through the winding of busy relay 325 to battery. Due to resistance 34| in the circuit relay 2|3 is not energized over the above traced circuit and the busy relay 365 operates to close only its X contact 10 at armature 334. When relay 306 deenergizes shortly after the second impulsing period, as previously described, said relay at armature 339 closes the circuit for fully energizing busy relay 325 from grounded conductor 259. Busy relay l5 335 now operates as previously described and connects busy tone to the calling line. The calling subscriber then hangs up to restore the link. In case the trunk line 8| is idle when called, then there is no ground on test conductor 281 20 and busy relay 305 is not energized. Now when relay 306 deenergizes shortly after the second impulsing period a circuit vis completed for energizing switchthrough relay 2 i3 in series with the cut-on relay of trunk line 8| as follows: from 25 grounded conductor 259, armature 331i and resting contact, armature 332, armature 3|?, conductor 239, upper winding of switchthrough relay 2|3, conductor 2li?, armatures 425 and 231, conductor 387, armatures 293 and 382, conductor 30 dal, and through the cut-off relay associated with this trunk line to battery. At armature 253 relay 2I3 closes its own locking circuit to ground at armature 3|8 and at armatures 24S and 23? disconnects the calling line from the 35 lait-hand windings of the repeating coil and connects the calling line to conductors 252 and 255 direct. At armature 228 relay 2|3 opens a point in the circuit to disconnect relay 293, at armature 259 disconnects ground from conductor 262 to open one of the multiple grounds to relay 30| and to open the locking circuit of relay 384. At armature 229 and working contact relay 2|3 grounds conductor 233 to complete an energizing circuit for relay i3d by way oi armature 4M, and 45 at armature 25| connects grounded conductor 2li to test conductor 382 by way oi armatures i4-5 and i3? to maintain the test conductor 331 grounded. Line relay 23? deenergizes when its circuit is opened at armatures 236 and 2li? and 50 at armature 233 opens the circuit to relay 303. Relay |383, upon energizing, at armatures 482 and 283 connects the trunk conductors 435 and 336 to the link conductors 252 and 255. Relay 363, upon deenergizing, at armature 325 opens the circuit of slow release relay 36| which deenergizes after an interval. The trunk equipment operates and connects ground to test conductor 'i hold relays 2|3, 322 and cut-oli relay 2 energized. The circuit for holding relay 60 253 energized extends from grounded conductor l-li, armatures S82 and 323, conductor 382, armatures 237 and 435, conductor ZIll, armatures 25| and 253, through the lower Winding of cutthrough relay 2&3 to battery. The circuit for 65 maintaining relay 332 in energized position extends irom grounded conductor 1381 over the previously traced circuit to armature 25| and thence over armatures 239 and 225 in multiple to conductor 2'i2 and through the winding of re- 70 lay 322 to battery. The circuit for maintaining cutol relay 2 in energized position is the same as that previously traced and extends from armature 2.5i by way of conductor 2TH, armature 222,

9, and through the winding of cut-off 2 to battery. The calling line conductors I4 and I5v are now both connected directly to the trunk conductors 485 and 485 whereby the calling sub- Talking battery to both the calling and called subscriber is furnished from the automatic eX- change.

After conversation and in response to the calling subscriber replacing his receiver, the switches in the automatic exchange release and discon nect ground from test conductor 481, thereby opening the holding circuit of relays 2 I3, 302 and cut oi relay 2. Relay 2I3, upon deenergizing, at armature 249 opens the circuit of relay 480. Cut-'off relay 2 deenergizes and opens the circuit to lock-out relay 3 and connects the line relay I to the line conductors of line I1. Slow to release relay 302deenergizes and at armature 322 opens the circuit to the nder relays I I0, II I and |01 and relays 204 and 202. At armature 323 relay 302 opens the circuit to connector relays 40| and 48|. Relay 480, upon deenergizing, at armatures 482 and 384 disconnect the talking conductors of the linkfrom the trunk line. The lock-out relay 3, the finder relays ||0, III, and |01 deenergize as previously described. Relays 204 and 202 deenergize and the latter relays connect the transerrelay 20| to the in lead 28|. Connector relays 40| and 48| likewise deenergize. In case the IN lead 28| is grounded transfer 20| is maintained energized, otherwise relay 20| rdeenergizes and the link may be used on sub-sequent calls.

Incoming trunk calls operate the link circuit the same as previously described for a local subscriber calling another local subscriber. In this case, however, reverse battery supervision is needed and when the local called subscriber answers relay 2 II energizes and at armature 243 closes the -circuit for battery reversing relay 209 to reverse batteryRoVer the calling trunk line.

Calls to ring-down trunks are made in the y same manner as described for called between local subscribers lines. On disconnect, however, it is necessary to transmit a disconnect signal over the ring-down trunk to signal the distant operator. After completion of conversation over a ring-down trunk the calling subscriber replaces his receiver to cause the deenergization of relay 201. At armature 230 relay 201 opens the circuit of relay 303 which deenergizes and at armature 321 disconnects battery through the winding of relay 2|I from the negative conductor 252 whereby battery is disconnected from the negative ring-down trunk conductor to cause the distant operator to receive a disconnect supervision. Relay 2H, upon deenergizing, at armature 243 opens the circuit to reversing relay 209 which deenergizes if operated and at armature 242 closes a holding circuit for slow to release relay 30| before the same deenergizes in response to the deenergization of relay 303. 'Ihis circuit maybe traced from Vground at armature'32l', conductor 255, armature 242 and resting contact, armature 245 and working contact, conductor 264, and through the winding of relay 30| to battery. The restoration of the link circuit is now controlled by the operator over the ring-down trunk. When the operator atthe distant end disconnects the circuit to relay 2I2 is opened and said relay deenergizes toopen the circuit of relay 30| rthe called subscriber disconnects.

at armature 245 to cause the deenergization of relay 30| and the release of the link as previously described.

Permanents 'Ihe link circuit is considered held by a-'permarient if it remains in a non-talking position for a minimum of two minutes after seizure or after Relays 580 and 590 and interrupter 593 in Fig. 5 comprise a 10 timing device for causing the operation of disconnect relay 206 if a fault, such as a permanent, appears. At two minute intervals interrupter contacts 593 are closed to complete a circuit for relay 590. At armature 592 relay 590 discon-l5 nects ground from conductor 284 and at the working contact of armature 592 completes an obvious circuit for energizing relay 580. At armature58| relay 580 prepares the circuit for connecting battery to conductor 285 to energize the 20 disconnect relay 20S if a permanent exists.

When interrupter spring 593 opens relay 590 deenergizes and at armature 59| momentarily connects battery to conductor 285 to energize disconnect relay 205 if a permanent exists. At arma- 25 ture 592 and its working contact relay 590A opens the circuit of relay 580 which deenergizes after an interval and at the resting contact of armature 592 grounds conductor 284. Relay 580, upon deenergizing, at armature 58| disconnects battery 30 from conductor 285.

In case the link is held by a permanent condition and the same is not in talking position, that is in case relays 2 I I, 2I2 vor 2I3 are not energized, a circuit is completed for disconnect relay 206 35 when relay 580 is energized and relay 590 deenergized as follows: kfrom grounded armature 32|, conductor 205, armatures 242, 245 and 248 and their resting contacts, winding of disconnect relay 206, normally closed springs controlled by ar- 40 mature 229, conductor 285, armatures 58| and 59|, resistance 594 to battery. Relay 200 at armature 228 disconnects the ground at the normally closed springs controlled by armature 228 and connects the ground on conductor 284 extending from the 45 resting contact of armature 592 to conductor 215 to maintain a holding condition on conductor 215 until the relay 590 is again operated. At armature 229 relay 200 opens a point in its original energizing circuit and completes a locking circuit 5o for itself over conductor 286. Now, in case the link circuit has not switched through to talking position by the energization of either relays 2| I, 2I2 or 2|3, before relay 590 again energizes, then relay 590 at armature 592 disconnects ground 55 from hold conductor 215 with the result that the link is released and the calling line is locked out. In case a calling subscriber fails to dial or the subscribers line is held by a short circuit the disconnection of ground from conductor 284 at 00 armature 592 opens the circuit to the finder relays such as IIO, III and |01 and the link control relays 202 and 204. Restoration of the finder relays disconnect the calling line from the link causing the deenergization of line relay 201 and (35 cut-off relay 2. At armature 22| relay 204 opens the circuit of relay 3I2 which thereupon deenergizes. At armature 2|1 relay 202 connects the transfer relay 20| to the in start lead 28|. Relays 20'1, 3I2 and 303 deenergize in the same 70 manner as previously described. Relay 303 at armature 325 opens the circuit of slow to release relay 30| which accordingly deenergizes and at .armature 3|8 opens the circuit for relay 302.

Relay`302 deenergizes and causes the release of 75 

